With mobile device product advancing all the time and process technology improving constantly, miniaturization for product size is of most concern for technology, such as metal-oxide-semiconductor field-effect transistor (MOSFET), which is miniaturized constantly. However, the miniaturization of the transistor derived many limitations and problems physically, such as hot-carrier injection, leakage current, insulation, short-channel effect and channel length control, such that the ability of the gate of the transistor to control the channel is gradually decreased.
Therefore, to solve the problems resulting from miniaturization of the transistor, multi-gate transistor is introduced to improve the ability of the gate to control the channel. Common multi-gate transistor is tri-gate transistor or gate-all-around transistor manufactured on the silicon substrate. However, the mobility of three-dimension isolation channel device still needs to be improved.
The prior technology, such as US publication No. US20100164101, disclosed that silicon germanium epitaxy wires surround the top of fin portion, so that the silicon germanium epitaxy wires are epitaxy wires with silicon core. Although the germanium nanowire could be formed by subsequent oxidation anneal process step to aggregate germanium to the center, the core has high silicon content, that is the nanowire has low germanium content, so as to affect the performance of the semiconductor device.